Spree bbk problems

[Ratrod]

Gotta a spree21 mm carb 48 mm bbk gears and pipe.. Stock oil pump. Along with 60:1 in the tank. Was running great .. Then I took the pump off and ran premix.. Ran ok for a day. Then it just wouldn't tune up . I put he pump back on and cut down the mix in tank. To the way it was before. It ran like crap so I checked everything. I put a new bbk kit cylinder rings base and head gasket. And spent about 10 hours today trying to tune it . From a 38 pilot to. A. 48 pilot. A 90 main to a 120 . Every time changing needle positions. And checking plugs. There was no point where it ran good too rich or too lean.. It did get better on the richer side but it was always it would bog or loose power somewhere on the throttle.. I have another spree with the same kit with a stock carb and it runs fine 35 plus mph. The only thing I have not replaced is the crankcase seal between the too halfs . Could this be my headache. I don't know. Someone help! Oh yeah the best it ever ran was with a 40 pilot and a 95 main clip one down.. Was perfect then

[Bear45-70]

Did you install a bigger main jet when you went to straight premix, if not you leaned your motor out.

Oh and ONE change at a time, otherwise the one good change can be negated by the bad change.

[Ratrod]

What exactly is leaning the motor out. Is it toast after that ?

[Bear45-70]

Did you do a compression check before you tore it apart? If not you were shooting in the dark.

Leaning out the engine means no enough gas cause the burn to be too hot, causing melted pistons and stuck rings.

[Ratrod]

I changed the rings and piston and still have the same problem.

[Bear45-70]

Do the simple obvious things before tearing the engine apart. Still do a compression check and a spark check. Change the spark plug.

[johnkiniston]

You might want to see if you can do a leakdown test.

http://www.youtube.com/watch?v=ySu2NC1X7s4 shows how to do one, You can borrow or build a tester.

[Bear45-70]

You might want to see if you can do a leakdown test.

http://www.youtube.com/watch?v=ySu2NC1X7s4 shows how to do one, You can borrow or build a tester.

A compression tester is cheaper and will tell you all you need to know. Leakdown testers are for racers.

[Ratrod]

Compression at 120.. Spark is good. Now what should. I do..

[Bear45-70]

It ran OK with a 98 main with pump and premix, and you went straight premix and jumped the main to 120? If so you are miles to rich. A jump to 100 or a 102 would have been more than enough. Same with the pilot, way to much change, a 40 or a 42 would be more reasonable.

[Ratrod]

I went through every size in between Those 90,92,95,100,102,105,110,115,120, going through the needle clip positions on each one before changing to a richer / leaner jet . As I did the same with the pilot and mix screw. There must be a small leak on the intake. So I will start with that and go from there ..

[speedy25]

Leakdown testers are for racers.

Hmmm, I guess you never used one before!

I use them all the time to make sure I'm not chasing my tail looking for a solution to a problem that cant be fixed externally.

OP- I think you are missing something with either a vacuum leak or something wrong in your carb. You should see MAJOR differences with the spread of jets you have installed.

-SP

[Bear45-70]

Leakdown testers are for racers.

Hmmm, I guess you never used one before!

I use them all the time to make sure I'm not chasing my tail looking for a solution to a problem that cant be fixed externally.

OP- I think you are missing something with either a vacuum leak or something wrong in your carb. You should see MAJOR differences with the spread of jets you have installed.

-SP

Only better than 500 hundred times and they never ever told me anything I had not learned with a compression test and a pull the head inspection. And that was the main reason we quit using them as everyday test gear. I used them many times on race motors to see if they were as good as it was after the last rebuild but when you are record hunting or on the championship trail every itty bitty micro horsepower helps but the expense of one over a stupid simple compression test can not be justified for what they tell you.